Hi,

maxim.cournoyer@gmail.com writes:

[...]

> It seems we're missing either a "vers" (doubtful) or more likely the
> "clientaddr" option.

It turns out that the "vers" (or more specifically, "nfsvers") option
was mandatory to resolve this error.  What "mount.nfs" from
nfs-utils seems to do is start with "4.2", then retry upon errors lesser
versions.

The attached patch adds the required "nfsvers=4.2" option by default, or
honors a user specified one.  No retry is done.  Note that it currently
uses file system options represented as an alist, but this is likely to
change as the code review on "allow booting from a Btrfs subvolume"
progresses (the current patch is based atop of
<https://bugs.gnu.org/37305>).

Maxim